Coriolis' Effect on Oceans

State Standards: GLEs/GSEs

National Standards:

Context of Lesson:

The lesson is designed to take the Coriolis Effect one step further, into the world of oceans. It is designed to show students the atmosphere's relationship with the main part of the hydrosphere.

Opportunities to Learn:

Depth of Knowledge

Prerequisite Knowledge

Plans for Differentiating Instruction

Accommodations and modifications

Environmental factors

Materials

Figure 11.11 page 251 from The Blue Planet for reference
Handout Figure 11.10 from The Blue Planet

Objectives:

You will be able to...

state evidence that the oceans have a pattern of movement
draw the difference between upwelling and downwelling
identify Ekman drift
describe how Ekman drift originates
Describe how up/downwelling originates
Direct an ignorant person on the reasoning behind movement of oceans because of the Coriolis effect

Instruction:

Opening:

Review of our discovery yesterday and the importance of it.
- Air is a fluid and it served as a transition from wind (or air, which we saw before as a gas) to the oceans (fluid). They are both fluids.
Quesiton 1 posed: What is the human population?
- Expected answer: 6.7 billion
  - http://www.census.gov/main/www/popclock.html is a good website to check this out at
Create a table, filling in human population 6.7 first, then 2.5 and have students guess if this is true

year	1950	2002
human population	2.5 billion	6.7 billion
global fish catch million tons/year	20	85

Don't fill in last row of table yet
Describe that during 1950s through 2002 there was an over exploitation of the marine fishery (now fill in 1950 and 2002 and the global fish catch)
Question 2 posed: What does this table shows us about population
- Expected answer: (it increased), so over exploitation was probably caused due to increase in population

Engagement:

Activity 1: Introducing the Fishing Industry

COD was one of main fishes that hasn't recovered from the over-exploitation, we even shut down factories along E coast from 1994 through 1998 and fish still hasn't recovered... considered a very complicated problem
it is a problem for New Englanders just as it is for Peruvians
Good fishing industry of the coast of Peru and Ecuador, as well as Oregon/California (have student find Peru on the globe).
Question 1 posed: Why are the oceans and marine fisheries being introduced?
- Trigger prior knowledge: Have them think back to what happens with uneven heating of atmosphere, creates wind and hot air which rises and creates fantastic wind patterns across the entire globe.
- Explain that these patterns can also be observed in ocean too because it is another fluid system. It is these patterns affect marine life.
Question 2 posed: Can anyone remember what this cycle of hot air rising and falling is called?
- Expected Answer: circuiation.
- We know that air circulates via Convection zones. Today, we will discover that water cirulates too, but through different means (write this in their notes).

Fluids	Air	Ocean
is part of the:	atmosphere	Hydrosphere
circulates by	convection cells	?

Write on the board: Observing and analyzing ocean currents can help you realize the effect of wind patterns on the ocean.

Activity 2: Discovering How the Coriolis effects the Ocean (Ekman drift)

There are surface currents (what we talked about, drives boats, surfing, how Christopher Columbus sailed over here) which are caused by the sun as we all know. But that is not the whole story... have hundreds of feet of water underneath you there is water moving below you as well. As wind creates friction against water, water creates friction against water beneath it. This creates little circles of rotation so water moves horizontally underneath a little bit too, just not as much as the top.
Does that make sense?
- Can someone think of an example where there are top layers that affect the bottom layers?
  - Expected answer: I would picture a 7-layered cake, with icing in the middle of each layer. If someone were to take the top layer and try to push it off the other 6 layers, the friction between the top and second layer would cause not just the top layer to move, but the 2nd, 3rd, 4th, and so on.
Create a diagram on the board of the following (use pg 250-251 The Blue Planet as a guide):
We are going to do a common sense activity. Picture the top 100 meters ocean are divided into, lets say, 3 layers of water.
- If wind is blowing parallel to the land, What will it do to the surface water (layer #1)?
  - Expected Answer: It fill pull the uppermost layers of water with it.
  - (Write question on board)
- What happens to the water directly underneath the surface water, layer #2?
  - Expected Answer: The surface water layer drags on the water immediately underneath it, setting that water in motion as well.
- What causes this movement:
  - Expected Answer: Friction.
- Will layer #2 move as fast as layer #3?
  - Expected Answer: No.
  - Why?
  - Because there is friction, the water underneath isn't exposed to the wind, so its only "push" is coming from the water, therefore it moves at a slightly slower speed.
- What will happen to layer #3?
  - Expected Asnwer: Slightly deeper, water will be pulled in that direction because of friction , but not as far.
- Everyone is doing great. Does this make sense so far?
  - Wait for questions and review if needed.
- What if I told you that all this is correct, but something else happens when we get deeper into the water. The water starts to move in a different direction. With each successive layer, it starts to move at a slightly different angle and by the time you reach 100 meters, the speed has dropped tremendously (no surprise) but the direction of the water has shifted 180 degrees so its going in a different direction than the wind!
- Can anyone give me a answer for this spinning? Hint: Think back to a couple classes that might have causes some other "fluid" to turn in different directions.
  - Expected Answer: Coriolis force actually veers the water in its path, and causes it to go towards the right
- We have just discovered the Ekman Spiral
  - Write Ekman Spiral above our numbered activity
- This spiral moves water, called...
  - Ekman transport: the average flow of surface water over the full depth of the spiral moves at about 90 degrees to the wind direction.
- But I just told you that it rotated 180 degrees, why is it only 90 degrees?
  - Expected answer: The spiral actually causes water to move in all different directions, but overall, the net flow of water through all the layers of surface water is in the direction 90 degrees from the wind.
- Encourage students to write this down in their notebook
- So if we go back to our main picture, when wind blows parallel to land, the Coriolis effect and the wind are actually contributing to this complex spiral in the surface waters
- If we are in the southern hemisphere, and wind is blowing North of the coast of Peru, which way is the water going to be pulled?
  - Expected answer: to the left, which would mean Ekman transport pulls water away from the coast towards the ocean.
  - Ekman drift is directly caused by the Coriolis effect, which pulls water just as it pulls the air because they are both fluids.
- Question 1 posed: We have just discovered how Ekman transport skews the direction of the water 90 degrees. Can anyone think of another instance where the Coriolis skews?
  - CONCLUSION: the Coriolis' effect on the hydrosphere (water) is very similar to that of the atmosphere (air)

Activity 2: Discovering Upwelling/Downwelling

Using Fig 11.11 pg. 251 as a guide, draw Upwelling and Downwelling on the board.
What happens when water pulls away from the land? Is there just an empty void there?

Expected Answer: water from very botttom comes up to replace this escaping water = upwelling

downdwelling, when water moves towards shore, surface water has no where to go but down underneath current and back out to sea

Have students draw a diagram in their notebook and write definitions next to them.
Explain that this movement creates a continuous cycle of rising/sinking water... that creates the currents underneath the ocean.
Question 3 posed:** What significance would upwelling and downdwelling have for the fishing industry?
- Allow students to brainstorm this idea of movement in the water. Without thinking of these two new vocabulary words, what would be beneficial for cycling of the water?
- Expected answer: With upwelling comes nutrients, which feeds fish populations which is why Peruvians have good fishing industry there

Activity 3: Tying location to the Tradewinds

That article below introduces El Nino, what if we hold on that and visit this first http://www.pfeg.noaa.gov/research/climatemarine/cmffish/cmffishery4.html which shows fisheries off the coast of Peru
or perhaps this is it
http://www4.ncsu.edu/~dbeggles/education/synergy/anchovy/asecoas.html

Question 1 posed: This entire class, we have been talking about the wind off the coast of Peru. Where is this wind coming from?
- Hints: Peru is near the equator, tradewinds are near the equator
  - Expected answer: The winds on the equator, tradewinds exist near Peru. The great fishing industry is caused by the tradewinds.
Hand out this article El Nino article in Peru
Ask students if they would like it to be read aloud by someone, and then see if there is a volunteer or I will read it.
Allow twenty minutes for students to read
While they are reading, write the following on the board.
- Respond to the questions...
  - What do you think is the most important part of this article and why?
  - Do you think you can personally relate to anything in this article and why?
  - How does this relate to upwelling and why would we be discussing it in science class? (written on board and responded to)
Allow ten more minutes for discussion and to see if students can verbally relate it to the class direct it towards upwelling and the disaster this might causewhy would this happen?
Introduce the trade winds once again and ask students if they remember them describe how they slacken upwelling reduced, fishing pop declines, birds die = local economic catastrophe sound familiar?? sounds like indonesia’s problem... the article I had you read
This is called El Nino

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